Seismic performance of high-strength concrete columns

Abstract

This experimental investigation was conducted to examine the behaviour of eight one-third scale columns made of high-strength concrete. The columns were subjected to a constant axial load corresponding to 30% of the column axial load capacity and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research are the volumetric ratio of transverse reinforcement (ρs = 1·58, 2·25%), tie configuration (Type H, Type C, Type D) and tie yield strength (fyh = 548·8 and 779·1 MPa). Test results show that the flexural strength of all the columns exceeds calculated flexural capacities based on the equivalent concrete stress block used in the current design code. Columns with 42% higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-02 showed ductile behaviour. With an axial load of 3% of the axial load capacity, it is recommended that the yield strength of transverse reinforcement be held equal to or below 548·8 MPa. Relationships between the calculated damage index and the observed damage such as initial crack, spalling of concrete, buckling of longitudinal bar, and crushing of concrete are proposed.